Wednesday, May 25, 2011

Greater detail makes HDR look good

HDR images are very pleasing, but have an unnatural look. Many of them remind me of the color rendering in Francis Ford Coppola's One from the Heart, filmed in the American Zoetrope studio, which produced also some of Wim Wender's movies with similar color rendering. The unnatural look comes from the dynamic range compression that is necessary to reproduce the images on media, I suspect mainly because the compression is only in luminance and not in chroma.

Regardless of the look, HDR images are very pleasing, and John McCann recently wrote the SPIE Newsroom article Human spatial processing accounts for dynamic range and color, in which he concludes:

At first, HDR imaging may have seemed best suited for improved recordings of scene radiances. However, glare limits the range of light that can be detected by cameras or the retina. All scene regions below middle gray are influenced, more or less, by the glare from the bright scene segments. Instead of accurate radiance reproduction, HDR imaging works well because it preserves the details in the scene's shadows. Spatial image processing preserves this information, but distorts accurate reproduction. Similarly, color constancy is the result of color comparisons of the entire scene.